Structural and mechanistic aspects of cytochrome c oxidase function will be examined. Particularly important will be infrared studies of ligand binding to the oxidase both isolated from and with the intact mitochondrion. Methods for heme a extraction from and reconstitution to the oxidase will be explored as will interactions of heme a with lipid and copper ions. Reactions of O2, CO, NO, N2, CN minus, N3 minus and NO2 minus with hemoglobins, myoglobins, other hemeproteins, and iron porphyrins will be explored.